The exclusive OR (XOR) gate is a device frequently used in logic circuits. Such devices obey the rule that the output assumes a high state if one, and only one, input assumes a high state. Conventionally, such devices are implemented electronically by any one of several arrangements of AND and OR gates, typically three in number, each of which in turn comprises several electronic components. While such an electronic XOR gate can be implemented as an integrated circuit which is much more compact than a device using discrete AND and OR gates, the large number of electronic elements required still occupy considerable real estate. Furthermore, conventional electronic XOR gates are relatively slow with limiting speeds in the neighborhood of a few hundred megahertz. Galium arsenide technology has extended this range to 1 to 2 gigahertz.
There are applications such as pseudorandom (PN) code generators which utilize XOR gates where it would be desirable to operate at much higher speeds, such as tens of gigahertz. To our knowledge, there are presently no XOR gates available that can operate at such speeds. While it is well known that optical data processing systems operate well into the gigahertz range, there is no known optical OR gate available.
Accordingly, there is a need for an XOR gate that can operate at high speed, and preferably at speeds well above one gigahertz.
There is also a need for an optical XOR gate which could be used with optical logic circuits operating at any data rate.
There is an attendant need for such an XOR gate which is inexpensive, reliable and occupies minimal real estate.
There is a further need for such an XOR gate which could be implemented either with discrete components or as an integrated circuit.
There is an additional need for such an XOR gate which can operate with any combination of electrical and optical inputs and outputs.